Effects of Total Dissolved Gas Supersaturation in Fish of Different Sizes and Species.

Xue Xue,Liang Liang,Li Li,Wang Wang

doi:10.3390/ijerph16132444

Abstract

Two endemic fish in the upper Yangtze River, the Rock Carp (Procypris rabaudi) and Prenant’s Schizothoracin (Schizothorax prenanti), were used as research objects in this study to assess the effects of total dissolved gas (TDG) supersaturation on fish of varying sizes. Fish were exposed to TDG-supersaturated water at the levels of 145, 140, 135, 130, and 125%. The results showed that fish swam slowly, responded clumsily, and then exhibited spiral swimming performance after a period of exposure to TDG-supersaturated water. Fish exhibited exophthalmos, body swelling, gill bleeding, and caudal fin bleeding when they died in the TDG-supersaturated water. With the increase in TDG supersaturation, the tolerance capacity of fish to supersaturated TDG significantly reduced. At high supersaturation, the difference in survival time between species was not significant, while fish with smaller sizes showed greater tolerance capacity. At low supersaturation, the tolerance capacity of fish was mainly affected by species, and the influence of size was relatively small. With the decrease in TDG supersaturation, the catalase (CAT) activity first increased and then decreased. Rock Carp displayed significantly less activity than Prenant’s Schizothoracin on exposure to TDG-supersaturated water. At high supersaturation levels, the CAT activity of Prenant’s Schizothoracin of small size was greater than that of large Prenant’s Schizothoracin. In contrast, small Prenant’s Schizothoracin showed less CAT activity at low TDG levels than did large individuals.

Highlights

Total dissolved gas (TDG) supersaturation is a physical condition in which the pressures of atmospheric gases in a solution exceed the barometric pressure [1], and this condition often occurs downstream of dams during the flood season [2,3,4] Large amounts of gases are taken into the downstream energy dissipation pool by high-speed turbulent water
Similar abnormal behavior existed in the fish at the TDG supersaturation levels of 125 and 130%, the behavior started a little later than that in fish at the levels of 145, 140, and 135%
This study considered two fish species, and the fish used from both species were juveniles

Summary

Introduction

Total dissolved gas (TDG) supersaturation is a physical condition in which the pressures of atmospheric gases in a solution exceed the barometric pressure [1], and this condition often occurs downstream of dams during the flood season [2,3,4] Large amounts of gases are taken into the downstream energy dissipation pool by high-speed turbulent water. The excess dissolved gas cannot be completely released within a short time due to the hydrostatic and hydrodynamic pressure in the energy dissipation pool, thereby resulting in TDG supersaturation in the downstream river water [5,6,7]. Endemic fish in the Columbia River of the United States suffered mortality caused by TDG supersaturation when hydropower structures discharged flows during the flood season [11,12,13]. Field observations have found that the TDG supersaturation downstream of these hydropower projects ranged from

Methods

Results

Discussion

Conclusion